Absorbent articles such as diapers, training pants, incontinence products, feminine hygiene products, swim undergarments, and the like, conventionally include a liquid permeable body-side liner, a liquid impermeable outer cover, and an absorbent structure. The absorbent structure is typically located between the outer cover and the liner for taking in and retaining liquids (e.g., urine) exuded by the wearer. The absorbent structure can be made of, for instance, superabsorbent particles. Many absorbent articles, especially those sold under the trade name HUGGIES™ by the Kimberly-Clark Corporation, are so efficient at absorbing liquids that it is sometimes difficult to tell whether or not the absorbent article has been insulted with a body exudate, especially when the absorbent article is being worn by a newborn or other very young wearers. Insult amounts in such wearers tend to be very small. Other wearers might also produce very small insults.
Accordingly, various types of moisture or wetness indicators have been suggested for use in absorbent articles. The wetness indicators include various passive indicators such as indicator strips, printing, or other devices within each absorbent article. Wetness indicators can also include alarm devices that are designed to assist parents or attendants in identifying a wet diaper condition early on. These devices produce either a visual or an audible signal.
Electronic insult/status detection in absorbent articles mainly depends on resistive, capacitive, inductive or optical sensors that are placed at the insult locations. All these sensors require either an electronic circuit that has to be directly in contact with the sensing electrodes, or conventional sensor components of limited effectiveness and range. These sensing electrodes placed at the insult locations can monitor the insult by measuring any changes in its resistance, capacitance or impedance characteristics. This makes it difficult to monitor the wetness/status of articles that are in intimate contact with the human body such as feminine hygiene products. Tampon users are often concerned with the status of the article. An efficient technology to monitor the status, fullness, and/or time-to-change status is still an unmet challenge.
Problems, however, have been encountered in designing a signaling device that can be used as desired but that does not appreciably increase the cost of each absorbent article, while providing a meaningful signal to the caregiver.